1. Field of the Invention
The present invention relates to a catheter assembly, and more particularly, concerns a catheter assembly with an air purging feature and its method of use.
2. Background Description
Catheters are used for a variety of medically related procedures. Such catheters, for example, balloon catheters, occlusion catheters, perfusion catheters, urinary and drainage catheters, and the like, often rely upon the use of an internal liquid to render the catheter functional for its desired procedure. Balloon catheters rely upon the pressure of a filling liquid to inflate or expand the balloon for the intended procedure. One such balloon catheter, known as an embolectomy/thrombectomy catheter, is utilized in the removal of blood clots from blood vessels. Representative examples of such embolectomy/thrombectomy catheters are disclosed in U.S. Pat. Nos. 4,351,341 and 3,467,101.
As the pressure of the filling liquid within the catheter increases during use, particularly if a balloon on the catheter is to be expanded, there is a possibility that the balloon may burst or the catheter tube may fail due to excess pressure of the liquid. If such bursting or failure occurs, the liquid inside the catheter will enter the blood stream of the patient. Normally, the pressurizing liquid is a saline or other physiologically inert solution which should not cause harm to the patient. However, should there be any air within the catheter, its bursting might release air into the patient's blood vessel with the possibility that an air embolus might be formed. Therefore, these catheters are typically purged of air prior to use so that only the liquid medium fills the catheter for its intended use.
It is a common technique to purge air from a catheter by creating a vacuum inside the lumen of the catheter, typically in conjunction with a syringe used for liquid filling purposes. As trapped air is released from the catheter, by a cumbersome hand manipulation and tapping procedure, the air is allowed to bubble into the syringe. The syringe is removed from the catheter in order to expel the air. Then, the syringe is reattached to the catheter filled with the liquid medium.
Such an air purging technique not only takes time, but involves a number of manipulative steps and exercises, and may require additional large size syringes other than those used for inflating the balloon. Moreover, there is a different degree of difficulty in purging air from catheters of smaller sizes or which have a construction which does not facilitate the air purging technique described above. There is, therefore, still a need for an improved air purging mechanism for those catheters which rely on a filling liquid for use. It is to such an improvement that the present invention is directed.